Electroless plating processes for room temperature deposition nickel

ABSTRACT

A metal alkoxide additive enhances deposit rate, stability and efficiency at room temperature of certain electroless nickel plating systems. These are systems which utilize hypophosphite as a reducing agent and as a source of phosphorous for strengthening the deposits. The additive apparently operates to: (a) significantly retard bath decomposition at room temperatures; (b) activate the hypophosphite reducing agent, which characteristically is poorly reactive at room temperature, thereby promoting higher reduction rates; and (c) promote more efficient utilization of the bath materials. The sequence and method of combination of bath ingredients materially affects the bath efficiency.

United States Patent [1 1 Bell et al.

[ Aug. 21, 1973 ELECTROLESS PLATING PROCESSES FOR ROOM TEMPERATURE DEPOSITION NICKEL Inventors: Harry F. Bell, Wappingers Falls;

David W. Rich, Poughkeepsie;

Matthew C. Smith, Pleasant Valley, all of NY.

International Business Machines Corporation, Armonk, N.Y.

Filed: May 6, 1972 Appl. No.: 241,586

Related 05. Application Data Continuation-impart of Ser. No. 124,590, March 15, 1971, abandoned.

Assignee:

US. Cl. 106/1, 117/47 A, 117/160 R Int. Cl. C231: 3/02 Field of Search 106/1; 117/47 A,

References Cited UNlTED STATES PATENTS 6/1970 Mallory et a1. 106/] Primary Examiner-Lorenzo B. Hayes Attorney-Robert Lieber et a1.

[57] ABSTRACT A metal alkoxide additive enhances deposit rate, stability and efficiency at room temperature of certain electroless nickel plating systems. These are systems which utilize hypophosphite as a reducing agent and as a source of phosphorous for strengthening the deposits.

The additive apparently operates to: (a) significantly 7 Claims, No Drawings ELECTROLESS PLATING PROCESSES FOR ROOM TEMPERATURE DEPOSITION NICKEL This is a Continuation-in-part of our Patent application, Ser. No. 124,590, filed Mar. 15, 1971, now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to processes and plating solutions for depositing nickel and related metals and alloys by autocatalytic chemical reduction in hypophosphite reduction baths under room temperature (e.g., 24 C/75 F) operating conditions.

2. Description of the Prior Art Hypophosphite reduction baths have been widely used in the past to produce uniform phosphorous strengthened deposits of nickel by electroless deposition. However, known baths having reasonably efficient plating rates must be operated and maintained at elevated temperatures (e.g., above 65 C/l50 F). One disadvantage of this is that when the deposit and substrate material have differing thermal coefficients of expansion relative to each other the plated product formed in the bath has a tendency to undergo exfoliation upon cooling.

On the other hand hypophosphite reduction baths which are known to be operable at room temperature have not been widely used due to inadequate deposition rate, non-uniformity of deposit accrual, inefficient utilization of materials or other objectionable disadvantage relative to elevated temperature processes.

The present invention avoids the foregoing disadvantages. With the disclosed additive dimensionally stable electroless deposits of nickel are obtained under room temperature operating conditions from baths containing hypophosphite as a reducing and phosphorous strengthening agent. In addition deposition rates, bath life and efficiency of utilization of materials are distinctively enhanced.

SUMMARY In carrying out the invention a quantity of a metal alkoxide is added to a bath containing a source (salt) of the metal (or alloy) to be plated, sodium hypophosphite as a reducing and deposit strengthening agent, and ammonium chloride as a buffer and complexing agent. The order of addition of bath ingredients is demonstrated to be quite important. The term metal alkoxide is used herein to characterize reaction products of certain metals with alcohols; in particular a metal in the class of metals consisting of sodium, potassium, lithium and barium reacted with any alcohol. Typical usage of this term in the art literature may be seen in Organic Chemistry" Third Edition, by Fieser and Fieser, at pages I24, I25 (Reinhold, 1957). Typical species of metal alkoxides are sodium methoxide (also termed sodium methylate) and sodium ethoxide (sodium ethylate).

The metal alkoxides have the form: MOCxI-Iy wherein M represents a metal in the class consisting of sodium, potassium, lithium and barium; and the radical OCxl-Iy represents the alkoxide constituent. Different species of metal alkoxide have different effects upon bath life, plating rate and different efficiency of consumption of bath materials. Specific species of designated alkoxides namely, methoxide, ethoxide, normal propoxide, iso-propoxide, normal butoxide and tertiary butoxide promote retardation of bath decomposition (i.e., extend bath life) under room temperature operating conditions. Individual species have associated basic or initial nickel deposition rates which remain constant for a specific constant concentration of hypophosphite ion. Thus, under operating conditions, the departure of the deposition rate from the basic rate is a function primarily of the relative concentrations of hypophosite ion and plating metal ion.

There appears to be an inverse relationship between basic plating rate and compexity of the alkoxide radical. Thus, the simpler methoxide (methylate) radical (OCH initiates and maintains a higher basic plating rate than the more complex ethoxide (ethylate) radical (OC H For example sodium methoxide (NaOCH added to a specific plating solution containing nickel chloride as the source of deposit material has an associated basic room temperature deposition rate of approximately 1 mil per hour for a specific concentration of sodium hypophosphite reducing agent. Sodium ethoxide (NaOC H in the same bath has a basic associated deposit rate of only 0.75 to 0.80 mils per hour.

Without the foregoing additive the nickel plating baths typically undergo spontaneous decomposition under room temperature conditions in periods on the order of 24-36 hours. With either the methoxide or ethoxide radical added decomposition is retarded for at least eight weeks under identical room temperature conditions.

The additive concentration does not appear to vary significantly during bath operation or at least it is not necessary to maintain or vary its concentration to achieve a specific basic deposition rate. Hypophosphite concentration and molar ratio of nickel ions to hypophosphite ions (Ni /H POJ) appear to be the most important factors in maintenance of plating rate.

It is among the objects of the present invention to provide an efficient method for depositing metals by hypophosphite reduction under room temperature operating conditions.

Another object is to provide a method of preparing electroless plating solutions suitable for efficient operation under room temperature conditions and contain.- ing hypophosphite ion as a reducing agent.

A feature of the invention involves the preparation of separate solutions (solutions A and B), one (e.g., solution A) containing the source of hypophosphite ion dissolved in the minimal volume of water required for solution and the other (solution B) containing all other bath ingredients exclusive of the source of alkoxide. It has been found that by adding the alkoxide source to the small volume solution and then combining the two solutions the efficiency of bath operation is materially enhanced in comparison to the efiiciency of operation attained when the alkoxide is simply added to the complete solution. It appears that in the latter situation the alkoxide may be interacting with the larger volume of water and separating by hydrolysis into inert constitu ents, whereas in the more concentrated situation (solution A), there may be a nucleophilic activating reaction between the alkoxide and hypophosphite.

Another feature of the invention :is that succinate ion can be added as an exaltant to the basic large volume solution, without adverse effect upon the alkoxide reaction, and provide thereby even further improvements in bath efficiency of operation at room temperature.

The foregoing and other objects and features of the invention will be more fully appreciated from the following detailed description.

DETAILED DESCRIPTION 25.0-30.0 gm/liter 45.0-55.0 gm/liter 30.0-50.0 gm/liter 16.0-20.0 gm/liter 2.7-21.6 gm/liter 2.7-21.6 gm/liter 2.7-2l.6 gm/liter to adjust pH to range 7-9 l8-50C Preferred Method of Preparation While almost any method of adding alkoxide to electroless plating solutions containing hypophosphite ion should be useful to provide stable and useful electroless deposition functions at room temperature, the most efficient rates of deposit are obtained when the following preferred procedure is utilized to prepare the bath.

Two solutions (A and B) are prepared. One (solution A) contains the sodium hypophosphite (NaH PO in a small volume of distilled water just sufficient to dissolve all of the hypophosphite. The other (solution B) contains the other ingredients of the complete bath exclusive of the alkoxide source (NaOCxHy) in the larger volume of distilled water required to establish the desired concentration of the bath. For the above example of 30.0-50.0 gms per liter of hypophosphite (assuming a final bath volume of 1.5 gallons) 50 milliliters of water is sufficient for solution A. According to the preferred practice of the present invention the alkoxide source ingredients are added to solution A and then the two solutions A and B are combined to make up the complete bath. When the alkoxide (e.g., methoxide) is added to the more highly concentrated solution A very little hydrolysis takes place. Instead there appears to be a strong nucleophilic reaction between the alkoxide and the hypophosphite which may generate hydride ion, a very powerful reducing agent.

If, to a greater extent the hydrolysis reaction is allowed to take place, the quantity of hydride ion (H') will fonn to a lesser extent and bath efficiency will be reduced. Consequently, it follows that the alkoxide and hypophosphite should be combined in a concentrated solution first and then diluted by addition to the more dilute solution containing the other bath constituents. Baths prepared in this manner have an order of magnitude (e.g., 4-5x) greater efficiency than baths prepared by the simpler method of adding the alkoxide to a dilute final solution.

Sodium Succinate (Na,C I-I O -6H,O) a known exaltant is employed in the solution to enhance even further the efficiency of the bath (especially rate of deposition). The unexpected aspect of this is that the alkoxide effects are in no wise diminished. It has been found that the percent exaltation is approximately 100 percent compared to a bath which does not contain this ingredient.

Approximate estimation of hypophosphite ion (H,PO,)' as determined by the nickel ion concentration.

The approximate value of NaI-I,PO,-I-I,O concentration in the solution can be estimated by knowing the exact concentration of nickel ion.

For the above examples, 30 gms/liter of NiCl,-6H,O and 45 gm/liter of NaH PO -H o provide a molar ratio of hypophosphite ion to nickel ion of about 3.25. For the same nickel chloride concentration of 30 gm/liter, and a smaller sodium hypophosphite concentration of 30 gm/liter, the molar ratio of (H,PO,)' to Ni reduces to about 2.3.

This molar ratio can be maintained fairly constant, providing that additions to the solution are made during the deposition cycle.

For the case above of 30 gm/liter NiCl,-6H O and molar ratio 3.25 the concentration of hypophosphite is calculated from:

yielding hypophosphite concentration in grams per liter:

44.01 gm/liter 0.61

This relationship can be approximately generalized over the above range as follows:

R 346.3(Ni

where R concentration of sodium hypophosphite expressed in grams per liter.

Proposed Theory of Operation The chemical reaction between the bath and substrate surface (the substrate may be of any material receptive to the deposit metal) is theorized to be:

It is theorized further that since the alkoxide (e.g., methoxide) radical is a strong nucleophilic agent the reaction is possibly one in which the methoxide radical attacks the hypophosphite nucleus replacing the hydrogen atoms by liberation of either hydrogen gas, hydrogen ions or hydride ions. In view of the high deposition rates indicated below it is believed that the hydride ion (H') may be an active intermediate species. Hydride ion is a very powerful reducing agent. Experimental observations indicate that bath pH remains fairly constant during the life of the solution indicating that hydrogen ions, which would normally be accompanied by increased acidity, are formed only to a very small extent if at all.

DISCUSSION OF RESULTS Tables below indicate rates of nickel deposition from various solutions (1% gallons if not otherwise noted) of above exemplary baths, with constituent parameters varied. Table 1 indicates deposit rates derived from the various exemplary alkoxide additives with indicated concentrations of nickel and hypophosphite salts.

TABLE I Alkoxide mils/hr. NiCl,-6H,O conc. NaH Poponc. TC NaOCH, 1.0 30 gm/liter 30 gin/liter 24 NaOC,H, 0.75-0.80 30 gm/liter 30 gin/liter 24 'Na0C,H, 0.60-0.70 30 gmlliter 30 gin/liter 24 None 0(see 30 grn/liter 30 gm/liter 24 (control) Table 7) Table 2 contains observations of bath effective life, in terms of mil/hr. average plating rate, under conditions of varying nickel ion to hypophosphite ion molar ratio. The individual plating rates were obtained from measurements of six successively plated samples immersed for progressively increasing intervals of time in a bath which was not supplemented by additions of consumed materials during the six platings.

TABLE 2** Elapsed plating mils/hr. Molar Ratio(Ni/H,PO{) time Sodium npropoxide 1% gallon solution; methoxide (NaOCH,) additive; no additions during plating; mils/hr. plating rate measured between elapsed times by weight gain method.

Table 3a below indicates the relationship in methoxide supplemented baths between deposition rate and varying hypophosphite concentration for a constant concentration of nickel salt. Table 3b indicates deposit rate under similar conditions for constant hypophosphite concentration and varying nickel concentration.

TABLE 3 (a) Concentration Concentration Mils per hour of Na H, P0, of Nichol-1,0 5 gm/liter 30 gm/liter 0.15 gm/liter 30 gm/liter 0.35 gm/liter 30 gm/liter 0.65 gm/liter 30 gm/liter 0.85 30 gm/liter 30 gm/liter 1.00 40 gm/liter 30 gm/liter 1.10 50 gm/liter 30 gm/liter 1.20

(b) Concentration Concentration Mils per hour" NiCl,-6H,O of Na H, PO, 5 gm/liter 30 gin/liter 0.85 10 gin/liter 30 gm/liter 0.85 15 gm/liter 30 gm/liter 0.85 20 gm/liter 30 gm/liter 0.90 gm/liter gm/liter 0.95 30 grn/liter 30 gm/liter 1.00

1 gallon solutions Calculated from weight gain per square inch Tables 4-7 indicate relationships between molar ratio of nickel ion to hypophosphite ion and plating rate, for progressively decreasing initial concentrations of methoxide additive. Control (zero methoxide added) is shown in Table 7.

TABLE 4 Molar ratio (Ni'/H,PO{) NaOCH, Mils/hr. 0.30 21.6 gmlliter 1.20 0.38 21.6 gm/liter 0.94 0.42 21.6 gm/liter 0.78 0.47 21 .6 gm/liter 0.44 0.49 21.6 gm/liter 0.29

TABLE 5 Molar ratio (Ni/H,PO,') NaOCl-l, Mils/hr. 0.30 13.5 gin/ iter 1.20 0.38 13.5 gmlliter 0.94 0.42 13.5 gm/liter 0.78 0.44 13.5 gm/liter 0.64 0.47 13.5 gmlliter 0.45 0.49 13.5 gm/liter 0.26

TABLE 6 Molar ratio (Ni/H,PO,') NaOCl-l, Mils/hr. 0.30 2.7 gmlliter 1.25 0.38 2.7 gm/liter 0.95 0.43 2.7 gm/liter 0.80 0.47 2.7 gm/liter 0.45 0.50 2.7 gm/liter 0.35

TABLE 7 Molar ratio (Ni*/H,PO,) NaOCH, Mils/hr. 0.30 0 gm/liter 0.09 0.38 0 gm/lilier 0.04 0.42 0 gm/liter 0.00(some deposition) 0.47 0 gm/liter 0.00( some deposition) 0.49 0 gm/liter 0.00(some deposition) Highest plating rate obtainable, commensurate with maintenance of bath stability, is seen to be inversely proportional to the molar 'ratio of Ni /H,PO This ratio should be between 0.35 and 0.29. The lower the molar ratio value, the greater the deposition rate. As plating occurs this ratio tends to become larger, and thus deposition rate falls off. The reason for the ratio becoming larger is due to the fact that H PO consumption is approximately 3X greater than that of nickel.

Therefore, addition to the solution of hypophosphite ion and nickel ion to replace consumed materials is extremely important. Based on analysis, these additions can be metered in via a proportioning pump.

Essentially, only nickel ion and hypophosphite ion, in the form of nickel chloride and sodium hypophosphite respectively, need be added to the solution during operation. Further additions of alkoxide during the useful bath life do not appear to be necessary. This also pertains to ammonium chloride, since chloride ion is supplied by the source of nickel ion and ammonium ions from the ammonium hydroxide.

. For comparison with the data of Tables 4-6 above obtained from baths prepared by the preferred method of combining alkoxide with an intermediate concentrated hypophosphite preparation and adding the concentrated mixture to a dilute preparation of the other plating ingredients Tables 8 to 10 below should be considered. Data in these tables was obtained from baths prepared by simple addition of indicated alkoxide species to an otherwise complete dilute solution of all other ingredients.

TABLE 8 1 wk gallon Molar ratio (Ni/H,PO{) NaOCH Mils/hr. 0.30 2.7 gm/lliter 0.70 0.38 2.7 gm/lliter 0.66 0.43 2.7 gm/lliter 0.57 0.48 2.7 gm/lliter 0.40 0.51 2.7 grn/lliter 0.27

TABLE 9 l 1% gallon Molar ratio (Ni*/H,PO{) NaOCH; Mils/hr. 0.30 21.6 grn/liter 0.70 0.37 21.6 gm/liter 0.65 0.44 21.6 gmlliter 0.57 0.47 21.6 gm/liter 0.39 0.50 21.6 gmlliter 0.29

TABLE 10 1 6 gallon (sodium methoxide added to fully dilute bath) Molar ratio Sodium succinate Mils/hr. l z fl 4 4 4 H: 0.30 20.0 gm/liter 0.90-1.12 0.38 20.0 gmlliter 0.75-0.91 0.43 20.0 gm/liter 0.67-0.75 0.48 20.0 gin/liter 0.51-0.57 0.51 20.0 gin/liter 0.37-0.44

Table 9 above indicates that increasing the methoxide concentration over the level specified in Table 8 has negligible effect upon deposition rate. Table 8 indicates significantly lower plating rate than Table 4. This suggests that the initial methoxide reaction with the reducing agent, which is the mechanism for promotion of deposit formation at room temperature, may be weakened or inhibited in a dilute system.

Table 10 above indicates the enhancement effect relative to Table 8 achieved by addition of sodium succinate to a bath prepared by addition of sodium methoxide to a fully diluted solution. Table 1 1 below indicates the further advance in plating rate achieved by adding the sodium succinate to a bath prepared by the preferred method of combination of a concentrated sodium methoxide/sodium hypophosphite solution with a dilute solution of other ingredients. It should be noted that the plating rate of Table l l exceeds the rate shown in Table 4 by a significant measure. The conclusion drawn from this is that exaltants such as succinate can be compatibly reacted in the presence of alkoxides with both ingredients promoting reduction and deposition of nickel.

TABLE 1 1 (Preferred method) 1 A gallon (alkoxide H PO added) Molar ratio Sodium succinate Mils/hr. (Ni/H,PO{) (Na,C H.O '6H,O

0.29 20.0 gm/liter 1.45-1.60 0.37 20.0 gin/liter 1.20-1.31 0.43 20.0 gin/liter 1054.15 0.48 20.0 gm/llter 0.60-0.70 0.50 20.0 gin/liter 0.470.52

Tables 12-15 below provide comparative deposition rate data for sodium n-propoxide and various ethylate species of the alkoxide genus (sodium ethoxide, lithium ethoxide, barium ethoxide). Solutions were prepared by the preferred two-step method previously outlined. Results, relative to the control information of Table 7, are taken to support the conclusion that each of the designated species of alkoxides provides significant promotional effects in room temperature nickel reduction systems of the type outlined above.

TABLE 12 Sodium n-propoxide (Ni"/H,PO{) Na(0C,l-l Milslhr. 0.30 4.15 gin/liter .70 0.31 4.15 gmlliter .67 0.45 4.15 g n/liter .60 0.47 4.15 gm/liter .41 0.50 4.15 gm/liter .22 0.30 0.0 gm/liter 0.10 (Ni/H,PO,') Na(OC,l-l,) Mils/hr. 0.30 33.2 gm/liter 0.69 0.37 33.2 gm/liter 0.65 0.44 33.2 gm/liter 0.59 0.48 33.2 gm/liter 0.42 0.50 33.2 gm/liter 0.20

TABLE 13 Sodium ethoxide (Ni/H,PO,') Na(OC,H,) Mils/hr. 0.30 3.4 gm/liter 0.81 0.37 3.4 gm/liter 0.77 0.44 3.4 gm/liter 0.72 0.47 3.4 gm/liter 0.40 0.50 3.4 gm/liter 0.27 0.30 0.0 gm/liter 0.10 (Ni/H,P0,') Na(OC,H.) Mils/hr. 0.30 27.0 gm/liter 0.80

0.37 27.0 gm/liter 0.76 0.44 27.0 gm/liter 0.70 0.47 2.0 gm/liter 0.39 0.50 27.0 gm/liter 0.25

TABLE 14 Lithium ethoxide (M ll-1,1 0,) Li(OC,H,) Mils/hr. 0.30 2.6 gmlliter 0.80 0.37 2.6 gm/liter 0.77 0.44 2.6 gm/liter 0.72 0.47 2.6 gm/liter 0.40 0.50 2.6 gm/liter 0.27 0.30 0.0 gm/liter 0.09

TABLE 15 Barium ethoxide (Ni/H,PO,') Ba(OC,H MilS/hr. 0.30 11.3 gm/liter 0.81 0.37 11.3 gm/liter 0.79 0.44 11.3 gm/liter 0.7l 0.47 11.3 gm/liter 0.40 0.50 11.3 gm/liter 0.27 0.30 0.0 gm/liter 0.20

Experimental observations suggest that the designated species of alkoxides do not enhance room temperature reduction of metals similar to nickel (e.g., iron and cobalt). However, deposits of nickel alloyed with these other metals, with predominance of nickel, are enhanced by the alkoxides (note Tables 16 and 17 below).

TABLE 16 Ni *+C0 */H,PO,' NaOCH; Mils/hr. 0.625 2.7 gm/liter 0.65 0.700 2.7 gm/liter 0.40 0.800 2.7 gm/liter 0.23

TABLE 17 Ni +Fe /H PO{ NaOCH; Mils/hr. 0.625 2.7 gm/liter 0.68 0.700 2.7 gin/liter 0.32 0.800 2.7 gmlliter 0.20

The following additional species of alkoxides have been compared as addition agents to the methoxide species: iso-propoxide, normal (n-) butoxide with sodium, tertiary (t-) butoxide with potassium, pnitrophenoxide with sodium, phenoxide (phenol) with sodium and p-benzyloxy(phenol). ln each instance a one liter bath of the basic plating solution without addition agent was divided into equal half liter portions, the two half-portions receiving equal proportions of the sodium methoxide additive and one of the abovementioned additional alkoxide species. The sodium methoxide bath was used as a unit reference for comparison of deposit accrual rates. Results of the comparison: the iso-propoxide is about 8/10 as effective as the methoxide; the nand tbutoxides are each approximately 6/10 as effective as the methoxide; and the pbenzyloxy, p-nitrophenoxide and phenoxide(phenol) additives are virtually ineffective (no observable deposit accrual).

Preparation of the substrate for deposition is varied according to the substrate material. For many materials e.g., glass, epoxy, paper the surface should be clean and pre-sensitized in a conventional sensitizing solution. For certain materials it may be necessary to precondition the surface if electrical continuity is to be assured.

In regard to electrical continuity it has been observed that all deposits obtained from foregoing electroless solutions on appropriately prepared surfaces are conductive, at least to the extent necessary to receive further electrolytic plating deposits.

We have shown and described above the fundamental novel features of the invention as applied to a preferred embodiment. It will be understood that various omissions, substitutions and changes in form and detail, of the invention as described herein, may be made by those skilled in the art without departing from the true spirit and scope of the invention. It is the intention therefore to be limited only by the scope of the following claims.

What is claimed is:

1. In an aqueous reduction bath for electroless deposition of nickel at room temperature (l8-50 C), comprising a soluble nickel salt, hypophosphite reducing agent and buffering and complexing agents, the improvement comprising maintaining in said solution a stabilizing and efficiency promoting amount of an addition agent comprising bath-soluble alkoxide selected from the group consisting of the methoxide, ethoxide, normal propoxide, iso-propoxide, normal butoxide and tertiary butoxide of a metal from the group consisting of sodium, potassium, lithium and barium.

2. A bath in accordance with claim 1 containing in addition a bath soluble source of succinate ion.

3. An aqueous electroless plating bath according to claim 1 containing sufficient amount of said alkoxide agent to yield plating rates in excess of 0.20 mils/hr.

4. A bath according to claim 1 in which the ratio of said nickel or nickel alloy ions to hypophosphite ions is maintained in the range 0.3-0.5] for nickel ions and in the range 0.625-0.800 for nickel alloy ions, by replenishment additions of sources of said ions.

5. A method of preparing a reduction bath for electroless deposition of nickel at room temperature (l8-50 C), comprising:

forming a first solution of hypophosphite reducing agent and alkoxide selected from the group consisting of the methoxide, ethoxide, normal propoxide, iso-propoxide, normal butoxide and tertiary butoxide of a metal from the group consisting of sodium, potassium, lithium and barium; said solution containing only sufficient water to dissolve said reducing agent and alkoxide;

forming a second solution containing a soluble nickel salt, buffering and complexing agents, and sufficient water to make said bath; and

combining said first and second solutions to form said bath.

6. A method of bath preparation in accordance with claim 5 in which said second solution forming step includes a substep of adding a soluble source of succinate ion to said second solution.

7. A method according to claim 5 in which said second solution forming step comprises provision of sufficient buffering agent in said second solution to establish pH in the range 7-9 in said reduction bath. 

2. A bath in accordance with claim 1 containing in addition a bath soluble source of succinate ion.
 3. An aqueous electroless plating bath according to claim 1 containing sufficient amount of said alkoxide agent to yield plating rates in excess of 0.20 mils/hr.
 4. A bath according to claim 1 in which the ratio of said nickel or nickel alloy ions to hypophosphite ions is maintained in the range 0.3-0.51 for nickel ions and in the range 0.625-0.800 for nickel alloy ions, by replenishment additions of sources of said ions.
 5. A method of preparing a reduction bath for electroless deposition of nickel at room temperature (18*-50* C), comprising: forming a first solution of hypophosphite reducing agent and alkoxide selected from the group consisting of the methoxide, ethoxide, normal propoxide, iso-propoxide, normal butoxide and tertiary butoxide of a metal from the group consisting of sodium, potassium, lithium and barium; said solution containing only sufficient water to dissolve said reducing agent and alkoxide; forming a second solution containing a soluble nickel salt, buffering and complexing agents, and sufficient water to make said bath; and combining said first and second solutions to form said bath.
 6. A method of bath preparation in accordance with claim 5 in which said second solution forming step includes a substep of adding a soluble source of succinate ion to said second solution.
 7. A method according to claim 5 in which said second solution forming step comprises provision of sufficient buffering agent in said second solution to establish pH in the range 7-9 in said reduction bath. 